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Catalytic Behavior of Mono‐ N ‐Protected Amino‐Acid Ligands in Ligand‐Accelerated C−H Activation by Palladium(II)
Author(s) -
Salazar Chase A.,
Gair Joseph J.,
Flesch Kaylin N.,
Guzei Ilia A.,
Lewis Jared C.,
Stahl Shan S.
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202002484
Subject(s) - catalysis , chemistry , palladium , ligand (biochemistry) , stereochemistry , pyridine , medicinal chemistry , carboxylate , turnover number , combinatorial chemistry , organic chemistry , receptor , biochemistry
Mono‐N‐protected amino acids (MPAAs) are increasingly common ligands in Pd‐catalyzed C−H functionalization reactions. Previous studies have shown how these ligands accelerate catalytic turnover by facilitating the C−H activation step. Here, it is shown that MPAA ligands exhibit a second property commonly associated with ligand‐accelerated catalysis: the ability to support catalytic turnover at substoichiometric ligand‐to‐metal ratios. This catalytic role of the MPAA ligand is characterized in stoichiometric C−H activation and catalytic C−H functionalization reactions. Palladacycle formation with substrates bearing carboxylate and pyridine directing groups exhibit a 50–100‐fold increase in rate when only 0.05 equivalents of MPAA are present relative to Pd II . These and other mechanistic data indicate that facile exchange between MPAAs and anionic ligands coordinated to Pd II enables a single MPAA to support C−H activation at multiple Pd II centers.